oldUsefulCode

    def loadMap(self, obj):
        print("loading Map...")
        global sand, ptdraw, pts
        self.painter.canvas.clear()
        sand = np.zeros((longueur,largeur))     
        ptdraw = ((np.loadtxt('sandMap.txt')).astype(int)).tolist()
        pnts = ptdraw
        pnts = np.array(pnts).reshape(int(len(pnts)/2), 2).tolist()
        #pnts = ((1,1), (5,5), (3,3) , (8,8), (4,4))
        sorted_list = dl.sort_pt(pnts)
        ptlinedraw = np.array(sorted_list).ravel().tolist()
        count = len(ptdraw)    # 3 rows in your example
        with self.painter.canvas:
            Color(0.8,0.0,0.2)
            Line(points = ptlinedraw)
            for i in range(0,count,2):
               pts = Point()
               sand[ptdraw[i]][ptdraw[i+1]]=1
               Color(0.8,0.7,0)
               pts.add_point(ptdraw[i],ptdraw[i+1])
               #pts.pointsize=1
               #pts.flag_update()